Question

Two successive reactions, $A\to B$ and $B\to C$ have yields of $80\%$ and $80\%$, respectively. What is the overall percentage yield for conversion of $A$ to $C$?

• A. $90\%$
• B. $80\%$
• C. $72\%$
• D. $64\%$

Answer 1

The correct option is D

$64\%$

Consider the inital moles of $A$ present in reaction is $1\text{mol}$.
For reaction: $A\to B$ Yield = 80%
Initial moles 1 0
After completion of reaction moles of B formed $=1\times \frac{80}{100}=0.8\text{mol}$

For reaction: $B\to C$ Yield = 80%
Initial moles 0.8 0
After completion of reaction moles of C formed $=80\times \frac{0.8}{100}=0.64\text{mol}$

Percentage yield for conversion of A to C $=\frac{\text{moles of C formed}}{\text{Initial moles of A taken}}\times 100$

$=\frac{0.64}{1}\times 100=64\%$